Ramona retired from the railroad after 40 years of service at age 72 in 2022. She is a widow and files as single. She received the Form RRB-1099 below. She received a Form RRB-1099-R with $18,250 in box 7 and reports it on line 5b of her Form 1040/1040-SR. She received no other taxable income. Up to _____ of her Tier 1 benefits may be taxable. (Answer choices are below the image.)